This proposal is for examination of some of the critical factors involved in the production and maintenance of the obese state. Specifically, the interactions of adipose cellularity, food intake, diet, spontaneous and forced exercise, hyperinsulinemia, and tissue resistance of muscle and adipose tissue will be studied in genetically obese and force-fed laboratory rodents. Thus, the sequence of events and their relative importance in the production and maintenance of obesity will be elucidated.